The invention concerns a fixation device for the stable connection of at least two bone portions of a broken bone, including at least one base body for tightly receiving at least one bone nail, at least one fixation rod which can be connected to the base body by means of a clamping joint, base body and fixation rod being released in a first connection state of the fixation device for adjusting their relative position and rigidly connected to each other by non-positive locking in a second connection state for fixing the adjusted position, a clamping holder which is mounted with adjustable angle on the base body and which receives a fixation rod for altering and adjusting its position in a receptacle, a bearing which mounts the clamping holder on the base body, and a connection to a tensioning rod on which the base body, the rod clamping holder and the bearing for the clamping holder are arranged in a row for tensioning relative to each other, wherein on the one hand the released connection is made when the tensioning rod connection is released, and on the other hand the stable non-positive locking connection is made when there is sufficient closing tension in the tensioning rod connection, wherein the rod clamping holder is formed by a holder which spherically displaces the fixation rod and which is guided in all spatial directions in a region for displacing and maintaining the set position on the base body, wherein the clamping holder and at least one bearing element of the bearing connecting the clamping holder to the base body are in a positive engagement which produces the spatial guidance, the tensioning rod passing through the bearing element. The invention also relates to a fixation element of such a device and a kit receiving its components in a sterile package.
A generic device which is also referred to as a fixator serves to make a fixation connection between bone portions in order to treat fractures. In particular, such fixators are applied in the case of fractures of the radius involving the wrist. Bone nails introduced into the bone portions must be rigidly connected to at least one fixation rod in order to allow the bone portions to grow together in the correct position relative to each other. According to the arrangement and alignment of the bone nails and the area to be bridged, the fixation rod must be capable of being aligned. In the aligned position, it must be capable of rigid connection to the base bodies which in turn can be fixed to the bone nails in a stable rigid connection.
A number of requirements are made of the fixators. High stability must be guaranteed. Fixed bones must not change their position relative to each other even when the fixator is worn for several weeks. This requires high stability particularly in the connections of individual components. The fixator is to be capable of being handled easily in order to shorten the operation time. Also, it is to be relatively light in weight. The fixation device is also to be cheaply available. This is especially important particularly with a view to disposable use when this is worthwhile compared with treating the components for reuse. Thus fixators which should be used several times as a result of high purchase costs are frequently not returned after they are used, so that a loss is incurred as a result. Also, special procedures and measures are necessary particularly for sterilisation in case of reuse.
Known fixators do not meet the above requirements. Fixation elements of a generic fixator include a base body having a rod clamping bearing which is spherically displaceable for positioning a fixation rod, wherein parts of the fixation element are connected by means of a tensioning rod (U.S. Pat. No. 5,393,161 A). A clamping holder ball is encased in a hinge joint. Consequently the fixation element is bulky, and handling is made more difficult. For the construction of a fixation device, screw clamps for bone nails and screw connections for fixation rods are necessary in addition. Fixation elements known from US 2003/109879 A1 are displaceable in only two planes for positioning a fixation rod in a screw connection. For displacement in other planes, additional parts with additional screw connections are provided. Clamping elements are arranged on different bearing axes. Other clamping holder devices having several screw connections on different bearing axes are relatively hard to handle when they are released, they tend to become released in the tensioned state, and they are made with relatively heavy clamping parts from metal. Fixators according to US 2003/109879 A1 and other known fixators provide one screw connection each for a number of bone nails and fixation rods. With these devices, handling is made particularly difficult, as a result of the plurality of screw connections there is a susceptibility to instability, and relatively solid metal elements are used for the screw connections in order to increase the rigidity of the connection.